ROLLUP - (MySQL Misc)
In MySQL, ROLLUP is a modifier used with the GROUP BY clause to generate subtotals for each level of grouping. In this tutorial, we'll discuss how to use ROLLUP in MySQL.
Syntax
The basic syntax for using ROLLUP with the GROUP BY clause is as follows:
SELECT column1, column2, SUM(column3)
FROM table_name
GROUP BY column1, column2 WITH ROLLUP;
The ROLLUP modifier is placed at the end of the GROUP BY clause.
Example
Let's say we have a table called "sales" with the following data:
| region | city | sales |
|---|---|---|
| East | Boston | 100 |
| East | Boston | 150 |
| East | NYC | 200 |
| West | LA | 300 |
| West | SF | 250 |
Now, let's say we want to display the sum of sales by region and city, as well as the total sum of sales for each region. We can use ROLLUP to achieve this:
SELECT region, city, SUM(sales)
FROM sales
GROUP BY region, city WITH ROLLUP;
This will produce the following output:
| region | city | SUM(sales) |
|---|---|---|
| East | Boston | 250 |
| East | NYC | 200 |
| East | NULL | 450 |
| West | LA | 300 |
| West | SF | 250 |
| West | NULL | 550 |
| NULL | NULL | 1000 |
The NULL values represent the total sum of sales for each region and all regions combined.
Explanation
In the example above, we used ROLLUP with the GROUP BY clause to generate subtotals for each level of grouping. We grouped the data by region and city, and then used the ROLLUP modifier to generate subtotals for each region and all regions combined.
The NULL values represent the subtotals generated by ROLLUP.
Use
ROLLUP is useful for generating subtotals for each level of grouping in MySQL. It can make it easier to analyze data and identify patterns.
Important Points
- ROLLUP can be useful for generating subtotals for each level of grouping in MySQL.
- The NULL values produced by ROLLUP represent the subtotals generated.
- ROLLUP can be used with multiple columns in the GROUP BY clause.
Summary
In this tutorial, we discussed how to use ROLLUP in MySQL to generate subtotals for each level of grouping. We covered the syntax, example, output, explanation, use, and important points of ROLLUP in MySQL. With this knowledge, you can now use ROLLUP in your MySQL queries to analyze data and identify patterns.